The present invention relates to a semiconductor device and a process for manufacturing it and, more particularly, to a technique which is effective if applied for switching the functions and word structures of a memory module including a plurality of semiconductor devices.
According to our investigations, the memory module to be used as an extended memory in a personal computer or a work station is constructed by mounting, on a module wiring substrate, a memory or a DRAM (dynamic random access memory) semiconductor device, made of a SOJ (small outline package) type resin-sealed package, for example.
In order that the memory module may have specifications conforming to the device to be used, there is mounted on the aforementioned module wiring substrate a memory in which the functions are switched in the refresh cycle, such as a refreshing operation cycle or a reading mode, such as FAST PAGE or EDO (extended data out).
The switching of these functions of the memory is executed by connecting a predetermined electrode in a semiconductor chip through a bonding wire with a supply voltage Vcc or a ground potential Vss or no connection terminal (NC) in the bonding step for packaging.
As another method of switching the afore-mentioned memory functions, moreover, there is known both a memory for selecting a predetermined reading mode in dependence upon a predetermined signal fed from the outside of the memory, as disclosed in Japanese Patent Laid-Open No. 75494/1984, and a memory for designating a bit length mode programmably on the basis of a predetermined signal, as disclosed in Japanese Patent Laid-Open No. 59682/1986. On the other hand, a memory module also is disclosed in Japanese Patent Laid-Open No. 334112/1994.
Incidentally, a memory extended system of this kind is disclosed in detail, for example, on pp. 114 to 126 of xe2x80x9cSemiconductor MOS Memory and Its Usexe2x80x9d, as issued on Aug. 30, 1990 by Nikkan Kogyo Shinbunsha and edited by Yasoji Suzuki. This publication describes the circuit construction and operations of a memory extending DRAM board.
Incidentally, it has been found by us that the aforementioned memory module has the following problem.
The memory, as used in a memory module to be used as the extended memory of a personal computer or the like, has a variety of function switching operations. However, the memory module, as mounted as a complete product on the module wiring substrate, cannot switch the functions. Thus, the memory modules are assembled for the individual functions, and there arises a problem that the degree of freedom for the production is degraded.
An object of the present invention is to provide a memory module, in which the individual functions and word structures can be arbitrarily switched outside of the package, and a process for manufacturing the memory module.
The aforementioned and other objects and novel features of the present invention will become apparent from the following description to be made with reference to the accompanying drawings.
A summary of the representative features of the invention to be disclosed herein will be briefly described in the following.
A memory module according to the present invention comprises at least one semiconductor device including function switching external terminals for selecting a function in dependence upon the state of a function switching signal; and a printed-wiring substrate with the semiconductor device mounted thereon and including function switching means for selecting an arbitrary function switching signal to be inputted to the function switching external terminals.
According to the present invention, moreover, the function switching means includes a first node formed on the printed-wiring substrate and electrically connected with the function switching external terminal of the semiconductor device, as mounted on the printed-wiring substrate; a second node formed on the printed-wiring substrate and connected with a supply voltage; and a third node formed on the printed-wiring substrate and connected with a reference voltage, and the function switching means is a means for switching the function switching signals altogether, as sinputted to the function switching external terminals, with or without conducting means provided between the first node and the second node or the third node.
According to the present invention, moreover, the function switching means is arranged at or in the vicinity of a corner portion of the printed-wiring substrate.
According to the present invention, moreover, the function of the semiconductor device to be switched by the function switching means includes a reading mode.
According to the present invention, moreover, the function of the semiconductor device to be switched by the function switching means includes a refresh cycle.
According to the present invention, moreover, the function of the semiconductor device to be switched by the function switching means includes a reading mode and a refresh cycle.
According to the present invention, moreover, the semiconductor device further includes word structure switching external terminals for selecting a word structure in dependence upon the state of a word structure switching signal, and the printed-wiring substrate further includes a word structure setting circuit for inputting a preset word structure switching signal to the word structure switching external terminals.
According to the present invention, a memory module comprises at least one semiconductor device including word structure switching external terminals for selecting a word structure in dependence upon the state of a word structure switching signal; and a dedicated printed-wiring substrate with the semiconductor device mounted thereon and including dedicated lines corresponding to the switched word structure of the semiconductor device.
According to the present invention, moreover, the memory module further comprises word structure switching means mounted on the dedicated printed-wiring substrate for selecting an arbitrary word structure switching signal to be inputted to the word structure switching external terminals.
According to the present invention, moreover, the word structure switching means includes a word structure setting circuit wired on the dedicated printed-wiring substrate and adapted to be switched to a predetermined word structure by mounting the semiconductor device so that a predetermined word structure switching signal is inputted to the word structure switching external terminals.
According to the present invention, moreover, the word structure switching means includes a fourth node formed on the dedicated printed-wiring substrate and electrically connected with the word structure switching external terminal of the semiconductor device, as mounted on the dedicated printed-wiring substrate; a fifth node formed on the dedicated printed-wiring substrate and connected with a supply voltage; and a sixth node formed on the dedicated printed-wiring substrate and connected with a reference voltage, and the word structure switching means is a means for switching the word structure switching signals altogether, as inputted to the word structure switching external terminals, with or without conducting means provided between the fourth node and the firth node or the sixth node.
According to the present invention, moreover, the semiconductor device further includes function switching external terminals for selecting a function in dependence upon the state of a function switching signal, and the dedicated printed-wiring substrate further includes function switching means for selecting an arbitrary function switching signal to be inputted to the function switching external terminals.
According to the present invention, moreover, the function switching means includes a first node (or electrode) formed on the dedicated printed-wiring substrate and electrically connected with the function switching external terminal of the semiconductor device, as mounted on the dedicated printed-wiring substrate; a second node (or electrode) formed on the dedicated printed-wiring substrate and connected with a supply voltage; and a third node (or electrode) formed on the dedicated printed-wiring substrate and connected with a reference voltage (or ground potential), and the function switching means is a means for switching the function switching signals altogether, as inputted to the function switching external terminals, with or without conducting means provided between the first node and the second node or the third node.
According to the present invention, moreover, the function of the semiconductor device to be switched by the function switching means includes a reading mode.
According to the present invention, moreover, the function of the semiconductor device to be switched by the function switching means includes a refresh cycle.
According to the present invention, moreover, the function of the semiconductor device to be switched by the function switching means includes a reading mode and a refresh cycle.
According to the present invention, moreover, the function switching means includes a function setting circuit wired on the dedicated printed-wiring substrate and adapted to be switched to a predetermined function by mounting the semiconductor device so that a predetermined function switching signal is inputted to the function switching external terminals.
According to the present invention, a process for manufacturing a memory module comprises the step of preparing a semiconductor device for selecting a predetermined word structure on the basis of a word structure switching signal, as inputted to word structure switching external terminals, and a plurality of kinds of dedicated printed-wiring substrates corresponding to a plurality of word structures, and selecting one of the dedicated printed-wiring substrates, corresponding to a demanded word structure of the semiconductor device, from the plurality of kinds of dedicated printed-wiring substrates; and the step of mounting the semiconductor device on the selected one of the dedicated printed-wiring substrates.
According to the present invention, moreover, a process for manufacturing a memory module comprises the step of preparing a semiconductor device for switching a word structure on the basis of a word structure switching signal, as inputted to word structure switching external terminals, and for selecting a function on the basis of a function switching signal, as inputted to function switching external terminals, function switching means for selecting an arbitrary function switching signal, as inputted to the function switching external terminals, with or without conducting means provided, and a plurality of kinds of dedicated printed-wiring substrates corresponding to a plurality of word structures, and selecting one of the dedicated printed-wiring substrates, corresponding to a demanded word structure of the semiconductor device, from the plurality of kinds of dedicated printed-wiring substrates; the step of mounting the semiconductor device on the selected one of the dedicated printed-wiring substrates; and the step of switching an arbitrary function selectively, with or without the conducting means provided.
According to the present invention, moreover, a process for manufacturing a memory module comprises the step of preparing a semiconductor device for selecting a predetermined word structure on the basis of a word structure switching signal, as inputted to word structure switching external terminals, and for switching a predetermined function on the basis of a function switching signal, as inputted to function switching external terminals, and a plurality of kinds of dedicated printed-wiring substrates corresponding to the switching operations of a plurality of word structures and a plurality of functions, and selecting one of the dedicated printed-wiring substrates, corresponding to a demanded word structure of the semiconductor device and the switching operation of the function, from the plurality of kinds of dedicated printed-wiring substrates; and the step of mounting the semiconductor device on the selected one of the dedicated printed-wiring substrates.
As described above, it is possible to improve the efficiency in the product development of the semiconductor device and to facilitate the product management thereby to reduce the cost.